Atomic layer deposition reactor for processing a batch of substrates and method thereof

ABSTRACT

The invention relates to a method that includes providing a reaction chamber module of an atomic layer deposition reactor for processing a batch of substrates by an atomic layer deposition process, and loading the batch of substrates before processing into the reaction chamber module via a different route than the batch of substrates is unloaded after processing. The invention also relates to a corresponding apparatus.

FIELD OF THE INVENTION

The present invention generally relates to deposition reactors. Moreparticularly, but not exclusively, the invention relates to suchdeposition reactors in which material is deposited on surfaces bysequential self-saturating surface reactions.

BACKGROUND OF THE INVENTION

Atomic Layer Epitaxy (ALE) method was invented by Dr. Tuomo Suntola inthe early 1970's. Another generic name for the method is Atomic LayerDeposition (ALD) and it is nowadays used instead of ALE. ALD is aspecial chemical deposition method based on the sequential introductionof at least two reactive precursor species to a substrate. The substrateis located within a reaction space. The reaction space is typicallyheated. The basic growth mechanism of ALD relies on the bond strengthdifferences between chemical adsorption (chemisorption) and physicaladsorption (physisorption). ALD utilizes chemisorption and eliminatesphysisorption during the deposition process. During chemisorption astrong chemical bond is formed between atom(s) of a solid phase surfaceand a molecule that is arriving from the gas phase. Bonding byphysisorption is much weaker because only van der Waals forces areinvolved. Physisorption bonds are easily broken by thermal energy whenthe local temperature is above the condensation temperature of themolecules.

The reaction space of an ALD reactor comprises all the heated surfacesthat can be exposed alternately and sequentially to each of the ALDprecursor used for the deposition of thin films. A basic ALD depositioncycle consists of four sequential steps: pulse A, purge A, pulse B andpurge B. Pulse A typically consists of metal precursor vapor and pulse Bof non-metal precursor vapor, especially nitrogen or oxygen precursorvapor. Inactive gas, such as nitrogen or argon, and a vacuum pump areused for purging gaseous reaction by-products and the residual reactantmolecules from the reaction space during purge A and purge B. Adeposition sequence comprises at least one deposition cycle. Depositioncycles are repeated until the deposition sequence has produced a thinfilm of desired thickness.

Precursor species form through chemisorption a chemical bond to reactivesites of the heated surfaces. Conditions are typically arranged in sucha way that no more than a molecular monolayer of a solid material formson the surfaces during one precursor pulse. The growth process is thusself-terminating or saturative. For example, the first precursor caninclude ligands that remain attached to the adsorbed species andsaturate the surface, which prevents further chemisorption. Reactionspace temperature is maintained above condensation temperatures andbelow thermal decomposition temperatures of the utilized precursors suchthat the precursor molecule species chemisorb on the substrate(s)essentially intact. Essentially intact means that volatile ligands maycome off the precursor molecule when the precursor molecules specieschemisorb on the surface. The surface becomes essentially saturated withthe first type of reactive sites, i.e. adsorbed species of the firstprecursor molecules. This chemisorption step is typically followed by afirst purge step (purge A) wherein the excess first precursor andpossible reaction by-products are removed from the reaction space.Second precursor vapor is then introduced into the reaction space.Second precursor molecules typically react with the adsorbed species ofthe first precursor molecules, thereby forming the desired thin filmmaterial. This growth terminates once the entire amount of the adsorbedfirst precursor has been consumed and the surface has essentially beensaturated with the second type of reactive sites. The excess of secondprecursor vapor and possible reaction by-product vapors are then removedby a second purge step (purge B). The cycle is then repeated until thefilm has grown to a desired thickness. Deposition cycles can also bemore complex. For example, the cycles can include three or more reactantvapor pulses separated by purging steps. All these deposition cyclesform a timed deposition sequence that is controlled by a logic unit or amicroprocessor.

Thin films grown by ALD are dense, pinhole free and have uniformthickness. For example, in an experiment aluminum oxide has been grownby thermal ALD from trimethylaluminum (CH₃)₃Al, also referred to as TMA,and water at 250-300° C. resulting in only about 1% non-uniformity overa substrate wafer.

General information on ALD thin film processes and precursors suitablefor ALD thin film processes can be found in Dr. Riikka Puurunen's reviewarticle, “Surface chemistry of atomic layer deposition: a case study forthe trimethylaluminum/water process”, Journal of Applied Physics, vol.97, 121301 (2005), the said review article being incorporated herein byreference.

Recently, there has been increased interest in batch ALD reactorscapable of increased deposition throughput.

SUMMARY

According to a first example aspect of the invention there is provided amethod comprising:

providing a reaction chamber module of an atomic layer depositionreactor for processing a batch of substrates by an atomic layerdeposition process; and

loading the batch of substrates before processing into the reactionchamber module via a different route than the batch of substrates isunloaded after processing.

In certain embodiments, the substrates comprise silicon wafers, glassplates, metal plates or polymer plates.

In certain embodiments, the batch of substrates (generally at least onebatch of substrates) is loaded from a different side of the reactionchamber module than the at least one batch of substrates is unloadedfrom the reaction chamber module. The loading and unloading may beperformed on opposite sides of the reaction chamber module or reactor.The loading and unloading may be performed horizontally.

In certain embodiments, the method comprises:

pre-processing the batch of substrates in a pre-processing module of theatomic layer deposition reactor;

processing the pre-processed batch of substrates by the atomic layerdeposition process in the reaction chamber module of the reactor; and

post-processing the processed batch of substrates in a post-processingmodule of the reactor, where the pre-processing module, the reactionchamber module, and the post-processing module are located in a row.

In certain embodiment, the modules have been integrated into a singledevice. In certain embodiments, there is a continuous route through themodules. In certain embodiments, the profile of each of the modules isthe same.

In certain embodiments, said processing by an atomic layer depositionprocess comprises depositing material on the batch of substrates bysequential self-saturating surface reactions.

In certain embodiments, said pre-processing module is a pre-heatingmodule and said pre-processing comprises pre-heating the batch ofsubstrates.

In certain embodiments, said post-processing module is a cooling moduleand said post-processing comprises cooling the batch of substrates.

In certain embodiments, the method comprises transporting the batch ofsubstrates in one direction through the whole processing line, theprocessing line comprising the pre-processing, reaction chamber andpost-processing modules.

In certain embodiment, the modules lie in a horizontal row. Thetransport mechanism through the modules is one-way through each of themodules.

In certain embodiment, pre-processed substrates are loaded into thereaction chamber module from one side of the module and the ALDprocessed substrates are unloaded from the module from the opposite sideof the module. In an embodiment, the shape of the reaction chambermodule is an elongated shape.

In certain embodiments, the pre-processing module is a first load lock,and the method comprises pre-heating the batch of substrates in a raisedpressure in the first load lock by means of heat transport.

The raised pressure may refer to a pressure higher than vacuum pressure,such as room pressure. Heat transport comprises thermal conduction,convection and electromagnetic radiation. At low pressures heat istransported through the gas space mostly by electromagnetic radiationwhich is typically infrared radiation. At raised pressure heat transportis enhanced by the thermal conduction through the gas and by convectionof the gas. Convection can be natural convection due to temperaturedifferences or it can be forced convection carried out by a gas pump ora fan. The batch of substrates may be heated by heat transport with theaid of inactive gas, such as nitrogen or similar. In certain embodiment,inactive gas is guided into the pre-processing module and said inactivegas is heated by at least one heater.

In certain embodiments, the post-processing module is a second loadlock, and the method comprises cooling the batch of substrates in araised pressure higher than vacuum pressure in the second load lock bymeans of heat transport.

In certain embodiments, the method comprises dividing the batch ofsubstrates into substrate subsets, and processing each of the subsetssimultaneously in the reaction chamber module, each subset having itsown gas flow inlet and gas flow outlet.

In certain embodiments, each subset are processed in a confined spaceformed be interior dividing walls.

In certain embodiments, the method comprises depositing aluminum oxideon solar cell structure.

In certain embodiments, the method comprises depositing Zn_(1-x)Mg_(x)Oor ZnO_(1-x)S_(x) buffer layer on solar cell structure.

According to a second example aspect of the invention there is providedan apparatus comprising:

a reaction chamber module of an atomic layer deposition reactorconfigured to process a batch of substrates by an atomic layerdeposition process; and

a loading and unloading arrangement allowing loading the batch ofsubstrates before processing into the reaction chamber module via adifferent route than the batch of substrates is unloaded afterprocessing.

The apparatus may be an atomic layer deposition reactor, an ALD reactor.

In certain embodiments, the apparatus comprises:

a pre-processing module of the atomic layer deposition reactorconfigured to pre-process the batch of substrates;

the reaction chamber module of the reactor configured to process thepre-processed batch of substrates by the atomic layer depositionprocess; and

a post-processing module of the reactor configured to post-process theprocessed batch of substrates, where the pre-processing module, thereaction chamber module, and the post-processing module are located in arow.

In certain embodiments, said processing by an atomic layer depositionprocess comprises depositing material on the batch of substrates bysequential self-saturating surface reactions.

In certain embodiments, said pre-processing module is a pre-heatingmodule configured to pre-heat the batch of substrates to a temperatureabove room temperature.

In certain embodiments, said post-processing module is a cooling moduleconfigured to cool the batch of substrates to a temperature below theALD process temperature.

In certain embodiments, the apparatus is configured for transporting thebatch of substrates in one direction through the whole processing line,the processing line comprising the pre-processing, reaction chamber andpost-processing modules.

In certain embodiments, the pre-processing module is a first load lockconfigured to pre-heat the batch of substrates in a raised pressure bymeans of heat transport.

In certain embodiments, the post-processing module is a second load lockconfigured to cool the batch of substrates in a raised pressure by meansof heat transport.

In certain embodiments, the reaction chamber module comprises partitionwalls or is configured to receive partition walls dividing the batch ofsubstrates into substrate subsets, each subset having its own gas flowinlet and gas flow outlet.

According to a third example aspect of the invention there is providedan apparatus comprising:

a reaction chamber module of an atomic layer deposition reactorconfigured to process a batch of substrates by an atomic layerdeposition process; and

means for loading the batch of substrates before processing into thereaction chamber module via a different route than the batch ofsubstrates is unloaded after processing.

Different non-binding example aspects and embodiments of the presentinvention have been illustrated in the foregoing. The above embodimentsare used merely to explain selected aspects or steps that may beutilized in implementations of the present invention. Some embodimentsmay be presented only with reference to certain example aspects of theinvention. It should be appreciated that corresponding embodiments mayapply to other example aspects as well. Any appropriate combinations ofthe embodiments may be formed.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example only, withreference to the accompanying drawings, in which:

FIGS. 1A-1J show a method of batch processing in a deposition reactor inaccordance with an example embodiment;

FIG. 2 shows a deposition reactor in accordance with an exampleembodiment;

FIG. 3 shows a carriage in another example embodiment;

FIG. 4 shows placement of substrates in a batch in accordance with anexample embodiment;

FIGS. 5A-5B show gas flow directions in accordance example embodiments;FIG. 6 shows a curved rectangular tube furnace in accordance with anexample embodiment;

FIG. 7 shows a curved rectangular tube furnace in accordance withanother example embodiment;

FIG. 8 shows a curved rectangular tube furnace in accordance with yetanother example embodiment;

FIG. 9 shows a rectangular tube furnace in accordance with an exampleembodiment;

FIG. 10 shows a rectangular tube furnace in accordance with anotherexample embodiment;

FIG. 11 shows a rectangular tube furnace in accordance with yet anotherexample embodiment;

FIG. 12 shows a round tube furnace in accordance with an exampleembodiment;

FIG. 13 shows a round tube furnace in accordance with another exampleembodiment; and

FIGS. 14A-14D show a method of a single batch processing in a depositionreactor in accordance with an example embodiment.

DETAILED DESCRIPTION

In the following description, Atomic Layer Deposition (ALD) technologyis used as an example. Unless specifically restricted by the appendedpatent claims, the embodiments of the present invention are not strictlylimited to that technology and to an equivalent technology, but certainembodiments may be applicable also in methods and apparatus utilizinganother comparable atomic-scale deposition technology or technologies.

The basics of an ALD growth mechanism are known to a skilled person.Details of ALD methods have also been described in the introductoryportion of this patent application. These details are not repeated herebut a reference is made to the introductory portion with that respect.

FIGS. 1A-1J show a method of batch processing in a deposition reactor inaccordance with an example embodiment. The deposition reactor comprisesa horizontal reaction chamber module 110, a tube furnace, which may havea rectangular cross-section, a curved rectangular cross-section, or around cross-section as shown in more detail with reference to FIGS.6-13. In other embodiments, the cross-section may be yet anothercross-section shape suitable for the purpose.

The reaction chamber module 110 comprises gates 111 and 112 atrespective ends of the module 110 for loading and unloading a carriage115 carrying substrate holders each carrying a batch of substrates 120.The gates 111 and 112 may open as shown in FIGS. 1A and 1H. Inalternative embodiments, the gates may be gate valves or similarrequiring very little space when opening and closing. In thoseembodiments, for example, a fixed or mobile pre-processing module can beattached to the module 110 on the side of gate 111. Similarly, inalternative embodiment, a fixed or mobile post-processing module can beattached to the module 110 on the side of gate 112. This is in moredetail described later in this description in connection with FIG. 2.

Each batch of substrates may reside in its own semiconfined space formedby flow guides or guide plates 121 which surround each of the batches onthe sides. Each semiconfined space therefore forms a kind of a box thathas at least partially open top and bottom side allowing exposure ofsubstrates in the box to process gases and removal of process gases fromthe box. The flow guides 121 may form a permanent structure of thecarriage 115. A substrate holder carrying a batch of substrates can betransferred into such a box by a loading robot or similar beforeprocessing. Alternatively, the flow guides 121 may be integrated to asubstrate holder. In those embodiments, and in other embodiments, arobot or similar may move a batch of substrates from a regular plasticwafer carrier cassette or substrate holder into a substrate holder (madeof aluminum, stainless steel or silicon carbide, for example) which cantolerate the processing temperatures and precursors of ALD. Thesesubstrate holders, which may have the flow guides 121 forming the boxwalls, are then loaded into the carriage 115.

The substrates 120 may be round substrate wafers as shown in FIG. 1A orrectangular wafers, square in particular, as shown in more detail laterin this description in connection with FIGS. 3-14D. Each batch mayconsist of wafers placed adjacent to each other to form a horizontalstack with open gaps between wafers as shown in more detail later inthis description in connection with for example FIGS. 4-5B.

The reaction chamber module 110 shown in FIGS. 1A-1J comprises precursorvapor in-feed lines 135 in an upper portion of the module. There may beone in-feed line for each precursor vapor. In the embodiment shown inFIGS. 1A-1J there are two in-feed lines which are horizontally adjacent.In other embodiments, the in-feed lines may be vertically adjacent. Someexamples on the placement of the in-feed lines have been shown in FIGS.6-13. Precursor vapor is fed to the in-feed line at least from onepoint. In other embodiments, in large reactors the in-feed line may beso long that it is advantageous to have more than one feed point of theprecursor vapor to the in-feed line, for example at both ends of thein-feed line.

There may be inlet openings in the in-feed lines allowing gases andvapors leave the in-feed lines and enter the reaction chamber. In anembodiment, the in-feed lines therefore are perforated pipelines. Theposition of the inlet openings depends on the embodiment. They may be,for example, in an upper and/or lower and/or side surface of the in-feedlines. The feedthrough of the in-feed lines into the reaction chambermay be implemented in various ways depending on the implementation. Onepossibility is to implement at least one feedthrough for each in-feedline through the ceiling of the reaction chamber. Another possibility isto implement at least one feedthrough for each in-feed line through aside wall of the reaction chamber.

The reaction chamber module 110 comprises an exhaust channel 136 belowthe support surface practically along the whole length of the module110. During processing, reaction by-products and surplus reactantmolecules are purged and/or pumped to a vacuum pump 137 via the exhaustchannel 136.

In an embodiment, the reaction chamber module 110 comprises at least oneheater heating the inside of the reaction chamber, that is, practicallythe reaction space. One possible heating arrangement is shown later inthis description in connection with FIGS. 14A-14D. The at least oneheater may be covered by a thermal insulator layer in directions otherthan the one pointing towards the reaction space.

The carriage 115 comprises wheels 117 or other moving means so that thecarriage 115 can move or slide into and inside the module 110 along atrack or rails 125 or along other support surface. The support surfacecomprises recesses 127 or other reception means for locking the carriage115 into a right position for processing. In the embodiment shown inFIGS. 1B and 1C the wheels 117 are lowered into the recesses 127. Thecarriage 115 may have lower guiding means or plates 122 in the area ofeach of the boxes that fit into the space 132 formed in the connectionor below the support surface.

In FIG. 1D, the carriage 115 is in the processing position inside themodule 110. The in-feed lines 135 are in fluid communication with theexhaust channel 136 and vacuum pump 137 through each of the boxeshousing the substrate batches.

Initially, the reaction chamber is in room pressure. The loading hatchor gate 111 which was opened during loading has been closed after thereaction chamber has been loaded with the batches of substrates 120. Thereaction chamber is then pumped into vacuum by the vacuum pump 137. Theloaded batches may have been pre-processed, for example, pre-heated intothe processing temperature range (meaning the actual processingtemperature or at least close to the processing temperature) in a fixedor mobile pre-processing module. Alternatively, they may be heated inthe reaction chamber.

Inactive purge (carrier) gas, such as nitrogen or similar, flows fromthe in-feed lines 135 into each of the boxes, as depicted by arrows 145.The balance between the flow rate of inactive purge (carrier) gas to thereaction chamber and the pumping speed of gas out of the reactionchamber keeps the reaction chamber pressure typically in the rage ofabout 0.1-10 hPa, preferably about 0.5-2 hPa during the depositionprocess.

A deposition process consists of one or more consecutive depositioncycles. Each deposition cycle (ALD cycle) may consist of a firstprecursor pulse (or pulse period) followed by a first purge step (orperiod), which is followed by a second precursor pulse (or pulse period)followed by a second purge step (or period).

FIG. 1E shows the first precursor pulse period during which thesubstrates are exposed to a first precursor vapor. The route of gas flowis from the in-feed line 135 into the boxes housing the substratebatches and via the exhaust channel 136 into the pump 137.

FIG. 1F shows the subsequent first purge period during which inactivegas flows through the reaction chamber and pushes gaseous reactionbyproducts and surplus precursor vapor to the exhaust channel 136 andfurther to the pump 137.

FIG. 1G shows the second precursor pulse period during which thesubstrates are exposed to a second precursor vapor. The route of gasflow is, again, from the in-feed line 135 into the boxes housing thesubstrate batches and via the exhaust channel 136 into the pump 137.

After a second purge period, the deposition cycle is repeated as manytimes as needed to grow a material layer of desired thickness onto thesubstrates 120.

In an example ALD deposition process, aluminum oxide Al₂O₃ is grown onbatches of substrates 120 using trimethyl aluminum TMA as the firstprecursor and water H₂O as the second precursor. In an exampleembodiment, the substrates 120 comprise solar cell structures onto whichaluminum oxide is grown. In an example embodiment, the processingtemperature is about 200° C.

After processing, the reaction chamber module 110 is reverted back intoroom pressure. The carriage 115 is raised from the recesses 127 as shownin FIG. 1H. And the carriage 115 is moved out of the reaction chambermodule 110 via the opened gate 112 as shown in FIG. 1J.

The embodiment shown in FIGS. 1A-1J thus illustrated a method of ALDbatch processing in which the batch(es) of substrates were loaded beforeprocessing into the reaction chamber module via a different route thanthe batch(es) of substrates were unloaded from the reaction chambermodule after processing.

In an alternative embodiment, the support surface (reference numeral125, FIG. 1A) may be omitted. Instead, there may be a mesh, a perforatedplate or a similar construction element in the carriage below the boxesextending along the area of each of the boxes so that the exhaustchannel is formed below the carriage. In this embodiment, the carriagecan be moved, for example, directly on the floor of the reaction chambermodule. This embodiment is shown in more detail later in the descriptionin connection with FIGS. 6-8.

In another alternative embodiment, the mesh can be attached to thesupport surface part. In this embodiment, the carriage can be moved onthe support surface but the carriage would not typically have the lowerguiding means or plates.

The embodiments in which a mesh is present can be implemented withoutforming the boxes at all. Instead the mesh can be designed such that thegas flow in the reaction space is as uniform as possible so that auniform growth on each surface of the substrates can be achieved. Forexample, the size of the openings in the mesh can be different dependingon the distance from a feedthrough conduit to the vacuum pump.

FIG. 2 shows a deposition reactor in accordance with another embodiment.However, what has been presented in the preceding in the connection ofFIGS. 1A-1F is by default applicable also to the embodiment presented inFIG. 2.

FIG. 2 shows a reaction chamber, a tube furnace, with three modulesmechanically coupled to each other. The reaction chamber module 110 maybasically be similar to that shown in the previous embodiments. In afirst side of the reaction chamber module 110 the reactor comprises apre-processing module 251. It may be a load lock that is mechanicallycoupled to the reaction chamber module 110 by the gate valve 111 orsimilar. After at least one batch of substrates has been loaded into thepre-processing module 251 via a hatch or gate 211 or similar, the atleast one batch of substrates can be pre-processed in that module 251.For example, the at least one batch of substrates can be pre-heated inthe pre-processing module 251 into the processing temperature range byheat transport. In an embodiment, inactive gas, such as nitrogen orsimilar, is conducted into the pre-processing module 251 from aninactive gas source. The inactive gas in the pre-processing module 251is heated by at least one heater 260 located in or in the outside of thepre-processing module 251. The at least one batch of substrates in thepre-processing module 251 is heated by the heated inactive gas by heattransport.

After pre-processing, the pre-processing module 251 is pumped intovacuum, the gate valve 111 is opened and the carriage or substrateholder carrying the pre-processed at least one batch of substrates ismoved into the reaction chamber module 110 for ALD processing.

In a second (opposite) side of the reaction chamber module 110 thereactor comprises a post-processing module 252. It may be a load lockthat is mechanically coupled to the reaction chamber module 110 by thegate valve 112 or similar. After processing, the gate valve 112 isopened and the carriage or substrate holder carrying the ALD processedat least one batch of substrates is moved into the post-processingmodule 252 for post-processing. For example, the processed at least onebatch of substrates can be cooled in the post-processing module 252 byheat transport. In an embodiment, inactive gas, such as nitrogen orsimilar, is conducted into the post-processing module 252 from aninactive gas source. The pressure of the post-processing module 252 canbe raised (into room pressure, for example) and the at least one batchof substrates in the post-processing module 252 is cooled by heattransport from the at least one batch of substrates comprising heatconduction through the inactive gas and natural and/or forced convectionof the inactive gas. The walls of the post-processing module can becooled for example with water-cooled piping. Warmed inactive gas can beconducted into an external heat exchange unit, cooled in the externalheat exchange unit and returned by pumping to the post-processing module252.

After post-processing, the hatch or gate 212 is opened and the carriageor substrate holder carrying the post-processed at least one batch ofsubstrates is moved out of the post-processing module 252.

The embodiment shown in FIG. 2 thus illustrated a modular depositionreactor. In an alternative embodiment, either of the pre- andpost-processing modules is omitted. In an alternative embodiment, thereis therefore implemented a deposition reactor substantially consistingof a pre-processing module and a reaction chamber module. And, in yetanother alternative embodiment, there is implemented a depositionreactor substantially consisting of a reaction chamber module and apost-processing module.

FIG. 3 shows the type of a carriage shown in FIGS. 1A-1J for carryingbatches of substrates in accordance with another example embodiment.Instead of carrying batches of round wafers, the carriage 115 shown inFIG. 3 is used to carry square shaped wafers. As shown in theenlargement of FIG. 4, the substrates can form horizontal stacks putboth horizontally and vertically next to each other. In the exampleshown in FIGS. 3 and 4, each batch of substrates has a 3×3 horizontalstack structure in which three horizontal stacks have been placed on topof each other and three such columns horizontally next to each other.The precursor vapor and purge gas flows along the surface of eachsubstrate vertically from top to bottom as shown in FIG. 5A. Inembodiments shown for example in FIGS. 9-11 the flow is a mainlyhorizontal flow along the surface of each substrate from left to rightor from right to left depending on the viewing angle as shown in FIG.5B.

FIGS. 6-11 show different design alternatives of the deposition reactorand deposition reactor modules in accordance with certain embodiments.

FIGS. 6-7 show side views of curved rectangular tube furnaces. In theembodiment shown in FIG. 6 the reaction chamber module 110 compriseshorizontally adjacent precursor vapor in-feed lines 135 a, 135 b,whereas in the embodiment shown in FIG. 7 the horizontal in-feed lines135 a, 135 b are vertically adjacent. Because ALD precursors aretypically reactive with each other, each precursor vapor flowspreferably along its dedicated in-feed line to the reaction chamber toprevent thin film deposition inside the in-feed line. A substrate holder660 in the carriage 115 carries a batch of square shaped substrates 120one of which is shown in FIGS. 6 and 7. The in-feed lines 135 a, 135 bhave openings on their upper surface via which precursor vapor and purgegas is deflected via the curved ceiling so as to generate a uniformtop-to-bottom flow along substrate surfaces. The carriage 115 has themesh (reference numeral 675) attached to it the function of which hasbeen discussed in the foregoing.

In the embodiment shown in FIG. 8, the reaction chamber module 110comprises additional inactive gas in-feed lines 835 in the top cornersof the module 110 to enhance purging of the reaction chamber. Flow rateof inactive gas along the additional inactive gas in-feed lines 835 canvary during the deposition process. For example, during the precursorpulse time the flow rate is low in inactive in-feed lines 835 tominimize inert gas shielding of the upper corners of the substrates andduring the purge time between the precursor pulses the flow rate is highin inactive in-feed lines 835 to enhance purging of the reactionchamber. Nitrogen or argon can be used as the inactive gas in mostcases. The in-feed lines 835 may be perforated pipelines having openingson their upper surface so that inactive gas initially flows in thedirection(s) shown in FIG. 8.

FIGS. 9-10 show side views of rectangular tube furnaces. A substrateholder or carriage 960 which can be horizontally moved within thereaction chamber module 110 carries a batch of square shaped substrates120 one of which is shown in FIGS. 9-10. In the embodiment shown in FIG.9 the reaction chamber module 110 comprises horizontally adjacentprecursor vapor in-feed lines 135 a, 135 b for producing horizontalprecursor vapor flow along substrate surfaces. The in-feed lines 135 a,135 b have openings on their side surface via which precursor vapor andpurge gas is deflected via a side wall 980 of the module 110. In thisway a uniform horizontal (left-to-right) flow along substrate surfacesis generated. The gas flow finally passes via a vertical mesh 975 intoan exhaust channel 936.

In the embodiment shown in FIG. 10 the reaction chamber module 110comprises additional inactive gas in-feed lines 1035 in the corners ofthe side wall 980 to enhance purging of the reaction chamber. Thein-feed lines 1035 may be perforated pipelines having openings on theirsurfaces so that inactive gas initially flows in the direction(s) shownin FIG. 11, that is, towards the corners.

FIGS. 12-13 show cross-sectional views of round tube furnaces. Asubstrate holder or carriage 1260 which can be horizontally moved withinthe reaction chamber module 110 carries a batch of square shapedsubstrates 120. In the embodiment shown in FIG. 12 the reaction chambermodule 110 comprises vertically adjacent horizontal precursor vaporin-feed lines 135 a, 135 b. The in-feed lines 135 a, 135 b have openingson their upper surface via which precursor vapor and purge gas isdeflected via the round ceiling so as to generate a uniformtop-to-bottom flow along substrate surfaces. The module 110 has the mesh(reference numeral 1275) on the bottom. The volume below the mesh 1275forms an exhaust channel 1236.

In the embodiment shown in FIG. 13, the reaction chamber module 110comprises additional inactive gas in-feed lines 1335 near the ceiling ofthe module 110 to enhance purging of the reaction chamber.

FIGS. 14A-14D show a method of batch processing in a deposition reactorin accordance with another example embodiment. The method shown in FIGS.14A-14D basically corresponds to the method shown with reference toFIGS. 1A-1J in the foregoing. The difference is that instead ofprocessing a plurality of batches at the same time, in the currentembodiment only a single batch is processed at the time. However, in theside direction, the batch on the carriage 1415 may be fairly longenabling hundreds or even thousands of substrates to be processedsimultaneously. The processing capacity can be increased by settinghorizontal stacks of substrates in rows and columns as shown in FIG. 14A(and in FIGS. 3 and 4 in the foregoing). Visible are also the at leastone heater (reference numeral 1461) heating the reaction space of thereaction chamber module 110 and the thermal insulation layer (referencenumeral 1462) covering the at least one heater 1461 in directions otherthan the one pointing towards the reaction space.

Otherwise the reference numbering and the operations in FIGS. 14A-14Dcorresponds to those used in FIGS. 1A-1J. FIG. 14A shows the loading ofthe carriage 1415 into the reaction chamber module 110 via gate 111.FIGS. 14B and 14C shows the lowering of the wheels of the carriage 117into the recesses 127 and the gaseous flow into the confined box housingthe substrates during processing. FIGS. 14D shows the unloading of theprocessed batch of substrates on the carriage 1415 via gate 112.

The foregoing description has provided by way of non-limiting examplesof particular implementations and embodiments of the invention a fulland informative description of the best mode presently contemplated bythe inventors for carrying out the invention. It is however clear to aperson skilled in the art that the invention is not restricted todetails of the embodiments presented above, but that it can beimplemented in other embodiments using equivalent means withoutdeviating from the characteristics of the invention.

Furthermore, some of the features of the above-disclosed embodiments ofthis invention may be used to advantage without the corresponding use ofother features. As such, the foregoing description should be consideredas merely illustrative of the principles of the present invention, andnot in limitation thereof. Hence, the scope of the invention is onlyrestricted by the appended patent claims.

1. A method comprising: providing a reaction chamber module of an atomiclayer deposition reactor for processing a batch of substrates by anatomic layer deposition process; and loading the batch of substratesbefore processing into the reaction chamber module via a different routethan the batch of substrates is unloaded after processing.
 2. The methodof claim 1, comprising: pre-processing the batch of substrates in apre-processing module of the atomic layer deposition reactor; processingthe pre-processed batch of substrates by the atomic layer depositionprocess in the reaction chamber module of the reactor; andpost-processing the processed batch of substrates in a post-processingmodule of the reactor, where the pre-processing module, the reactionchamber module, and the post-processing module are located in a row. 3.The method of claim 2, wherein said processing by an atomic layerdeposition process comprises depositing material on the batch ofsubstrates by sequential self-saturating surface reactions.
 4. Themethod of claim 2, wherein said pre-processing module is a pre-heatingmodule and said pre-processing comprises pre-heating the batch ofsubstrates.
 5. The method of claim 2, wherein said post-processingmodule is a cooling module and said post-processing comprises coolingthe batch of substrates.
 6. The method of claim 2, comprisingtransporting the batch of substrates in one direction through the wholeprocessing line, the processing line comprising the pre-processing,reaction chamber and post-processing modules.
 7. The method of claim 2,wherein the pre-processing module is a first load lock, and the methodcomprises pre-heating the batch of substrates in a raised pressure inthe first load lock by means of heat transport.
 8. The method claim 2,wherein the post-processing module is a second load lock, and the methodcomprises cooling the batch of substrates in a raised pressure in thesecond load lock by means of heat transport.
 9. The method of claim 1,comprising dividing the batch of substrates into substrate subsets, andprocessing each of the subsets simultaneously in the reaction chambermodule, each subset having its own gas flow inlet and gas flow outlet.10. The method of claim 1, comprising depositing aluminum oxide on solarcell structure.
 11. An apparatus comprising: a reaction chamber moduleof an atomic layer deposition reactor configured to process a batch ofsubstrates by an atomic layer deposition process; and a loading andunloading arrangement allowing loading the batch of substrates beforeprocessing into the reaction chamber module via a different route thanthe batch of substrates is unloaded after processing.
 12. The apparatusof claim 11, comprising: a pre-processing module of the atomic layerdeposition reactor configured to pre-process the batch of substrates;the reaction chamber module of the reactor configured to process thepre-processed batch of substrates by the atomic layer depositionprocess; and a post-processing module of the reactor configured topost-process the processed batch of substrates, where the pre-processingmodule, the reaction chamber module, and the post-processing module arelocated in a row.
 13. The apparatus of claim 12, wherein said processingby an atomic layer deposition process comprises depositing material onthe batch of substrates by sequential self-saturating surface reactions.14. The apparatus of claim 12, wherein said pre-processing module is apre-heating module configured to pre-heat the batch of substrates. 15.The apparatus of claim 12, wherein said post-processing module is acooling module configured to cool the batch of substrates.
 16. Theapparatus of claim 12, wherein the apparatus is configured fortransporting the batch of substrates in one direction through the wholeprocessing line, the processing line comprising the pre-processing,reaction chamber and post-processing modules.
 17. The apparatus of claim12, wherein the pre-processing module is a first load lock configured topre-heat the batch of substrates in a raised pressure by means of heattransport.
 18. The apparatus of claim 12, wherein the post-processingmodule is a second load lock configured to cool the batch of substratesin a raised pressure by means of heat transport.
 19. The apparatus ofclaim 11, wherein the reaction chamber module comprises partition wallsor is configured to receive partition walls dividing the batch ofsubstrates into substrate subsets, each subset having its own gas flowinlet and gas flow outlet.